JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<div ng-app="app">
    <div ng-controller="ctrl">
        <textarea watcher ng-model="expression"></textarea>
    </div>
</div>

JavaScript

var app = angular.module('app',
    [
    ]);

app.directive('watcher', [function () {
    return {
        restrict: 'A',
        link: function (scope, elem, attrs) {
          scope.$watch(attrs.ngModel, function (v) {
                if(v) {
                    console.log('I has value!');
                } else {
                    console.log('I has no value :(');
                }
            });
        }
    }
}]);

app.controller('ctrl', ['$scope', function($scope) {

}]);